The present invention relates to an electrostatic transportation device, a development device and an image formation apparatus.
As an image formation apparatus such as a reproducing machine, a printer, a facsimile or the like, there is one where a latent image is formed on a latent image carrier using an electrostatic photographic process, developer (hereinafter, referred to as toner, too) as a fine particle is attached to the latent image to develop the latent image and visualize the latent image as a toner image, and an image is formed by transferring the toner image onto a recording medium (including an intermediate transferring member).
In such an image formation apparatus, as a development device for developing a latent image, there has been conventionally known one where toner which is stirred in a development device is carried to a surface of a developing roller which is a developing agent carrier, the toner is transported to a position opposed to a surface of a latent image carrier by rotating the developing roller, the latent image of the latent image carrier is developed, toner which has not been transferred to the latent image carrier is recovered in the development device after the development by rotation of the developing roller, toner is newly stirred/charged and carried and transported.
Also, as the image formation apparatus, there has been known one where developing is carried out by a so-called jumping developing system where toner is transferred from a developing roller to a latent image carrier with non-contact, as described in Japanese Patent Application Laid-Open (JP-A) No. 09-197781 and JP-A 09-329947.
Further, as the image formation apparatus, there has been known one where toner is transported on a developing roller surface using electrostatic force, toner is separated from the developing roller surface by attracting force occurring between the toner and a latent image carrier to be attached to a latent image carrier surface, as described in JP-A 05-19615, or one where toner is transported at a position opposed to a latent image carrier using a transporting base plate for transporting toner with electrostatic force, and the toner is separated from a transporting surface with attracting force occurring between the latent image carrier and the toner to be attached to a surface of the latent image carrier, as described in JP-A 59-18375 or the like.
Also, as another image formation apparatus, there has been known a flying type (toner jetting type) image formation apparatus where a control electrode is disposed between a developing roller carrying toner and a recording medium and a back electrode is disposed behind the recording medium, toner is made flyable in a direction of the recording medium by generating electric field between the back electrode and the developing roller, and an image is formed on the recording medium by selectively controlling the flying of toner with the control electrode, as described in JP-A 11-170591, JP-A 11-115235 and JP-A 11-179951.
Also, as fine particles transporting apparatus for transporting fine particles such as toner particles, there has been one where fine particles are transported using spatial travelling-wave field, as described in JP-A 07-267363. This apparatus is structured such that a spatial travelling-wave field is formed around an electrode by applying a driving voltage to the electrode and repelling force and driving force act and charged fine particles by the travelling-wave field so that the fine particles are transported in a travelling direction of the field. As a classifying apparatus for classifying fine particles such as toner particles or the like using this spatial travelling-wave field, there has been proposed one where classification (fractionation) is performed by applying electrostatic force, weight, centrifugal force or the like to the fine particles, as described in JP-A8-149859.
However, in the image formation apparatus provided with the development device applying toner to a latent image carrier using the developing roller, or the flying type image formation apparatus where toner is carried on a developing roller and the toner is flied from the developing roller to a recording medium by controlling an electric field, toner invades a space between the developing roller and a side plate of the development device, in which the toner is rubbed and toner solidification occurs, which results in adverse influence on an image, or a seal member around the development device has been degraded according time elapse, toner is scattered by stirring/charging the developer or toner in the development device, which results in a background dirt of an image.
Furthermore, when toner has been charged by frictional charging or charging due to corona discharging, saturated charged toner section and unsaturated charge toner section exist in a mixed manner so that the toner has a large charge distribution. When such toner is forcibly transferred to a developing roller using a magnetic brush or a transferring roller, toner section of the toner which has been once carried on the developing roller is detached from the developing roller in a state where a developing speed of the developing roller is a speed (linear speed of 100 cm/VHF or so) so that toner may be scattered or a background for a formed image becomes dirty easily.
Further, in the development device which performs the so-called jumping development, since delivery and reception of toner which has been charged with a high voltage must be performed, there is a problem that a high voltage power source is required, which results in large-sizing of an apparatus and increase in cost.
On the other hand, the present inventors have studied the conventional electrostatic transportation device which transports toner using an electrostatic force obtained by a spatial travelling-wave field and they have found that, in the conventional electrostatic transportation device where each of a plurality of electrodes is set to be 150 to 250 xcexcm and an interval between the electrodes is set to be 250 to 500 xcexcm, toner stays in a mountain manner between the adjacent electrodes so that stable toner transportation can not be achieved effectively.
Also, when toner is transported by an electrostatic force, since toner particles are different in size and shape, there is such a problem that it is difficult to achieve a stable transportation, it is required to achieve matching between the toner and the charging member in the conventional electrostatic transporting apparatus, and so on.
It is an object of the invention to provide an electrostatic transporting apparatus which allows stable and efficient transportation and hopping of fine particles and provide a development device and an image formation apparatus where, using ETH (Electrostatic Transport and Hopping) phenomenon, configuration can be simplified and cost reduction can be achieved, a low voltage driving is allowed, and a high image quality can be obtained.
The ETH phenomenon means a phenomenon where fine particles are applied with energy of phase-shifting field, the energy is transformed to mechanical energy, and the fine particles themselves fluctuate dynamically. The ETH phenomenon is a phenomenon including movement (transportation) of fine particles in a horizontal direction due to electrostatic force and movement (hopping) of fine particles in a vertical direction due to electrostatic force, and it is a phenomenon where fine particles jump on an electrostatic transporting base plate with a component of a travelling direction due to a phase-shift field. A phenomenon utilizing the ETH phenomenon is called ETH phenomenon.
When behaviors of fine particles on a transporting base plate are expressed in a distinguishing manner, xe2x80x9ctransportationxe2x80x9d, xe2x80x9ctransporting speedxe2x80x9d, xe2x80x9ctransporting directionxe2x80x9d and xe2x80x9ctransporting distancexe2x80x9d are used for movement of a horizontal direction to a transporting body, and xe2x80x9choppingxe2x80x9d, xe2x80x9chopping speedxe2x80x9d, xe2x80x9chopping directionxe2x80x9d and xe2x80x9chopping height (distance)xe2x80x9d are used for fly (movement) of in a vertical direction to the transporting body. Incidentally, xe2x80x9ccarryxe2x80x9d included in the terms xe2x80x9celectrostatic transportation devicexe2x80x9d and xe2x80x9ccarrying bodyxe2x80x9d is synonymous with xe2x80x9cmovementxe2x80x9d.
According to one aspect of the present invention, there is provided an electrostatic transportation device comprising a transporting base plate having a plurality of electrodes which generate a electric field which performs carrying and hopping of fine particles by electrostatic force, wherein the width of each electrode in a travelling direction of fine particles is set to be in a range of 1 time to 20 times an average particle diameter of the fine particles, the pitch between adjacent electrodes in the travelling direction of fine particles is set to be in a range of 1 time to 20 times the average particle diameter of the fine particles, and driving waveforms of n phases or more (n is an integer of 3 or more) are applied to respective electrodes. Incidentally, the term xe2x80x9ctravelling directionxe2x80x9d means a direction of the fine particles moving along the transporting base plate. Also, the term xe2x80x9cfine particlesxe2x80x9d is used to include xe2x80x9cparticle or granulexe2x80x9d, xe2x80x9cfine particle or granulexe2x80x9d, xe2x80x9cpowderxe2x80x9d, xe2x80x9cfine powderxe2x80x9d, xe2x80x9cpowder bodyxe2x80x9d, xe2x80x9cfine powder bodyxe2x80x9d and the like.
Also, according to another aspect of the present invention, there is provided an image formation apparatus comprising: an electrostatic transportation device according to the present invention which has a transporting base plate which transporting fine particles towards a developing section by electrostatic force; an electrostatic transportation device according to the present invention which has a transporting base plate which performs hopping of fine particles in the vicinity of the latent image carrier by electrostatic force; or an electrostatic transportation device according to the present invention which has a transporting base plate which transports fine particles towards a developing section by an electrostatic force; and an electrostatic transportation device according to the present invention which has a transporting base plate which performs hopping of fine particles in the vicinity of an image carrier by an electrostatic force.
According to still another aspect of the present invention, there is provided a development device comprising: an electrostatic transportation device according to the present invention which has a transporting base plate which transporting fine particles towards a developing section by electrostatic force; an electrostatic transportation device according to the present invention which has a transporting base plate in the vicinity of an image carrier by electrostatic force, or an electrostatic transportation device according to the present invention which has a transporting base plate which transports fine particles towards a developing section by an electrostatic force; and an electrostatic transportation device according to the present invention which has a transporting base plate which performs hopping of fine particles by an electrostatic force.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.